Quantification of water table dynamics is an essential part of eco-hydrological characterisation as they are a controlling factor for vegetation and groundwater-dependent ecosystems. This is often done using the concept of groundwater depth classes, which are defined based on mean high winter and mean low summer water levels. However, this concept does not consider inter-yearly variability of groundwater levels. Also, groundwater depth classes can depend strongly on local topography, which is specially the case in dune belts in coastal regions. In this paper, the relation between groundwater depth classes and the size of seasonal and inter-yearly variations is investigated in a dune region along the Belgian coast, which has the special hydrological and ecological feature of including a dune river. The spatial pattern of the seasonal fluctuations and inter-yearly variability here is much simpler than the heterogeneous distribution of groundwater depth classes. This may provide additional useful information in relation to the occurrence of vegetation and can be used in the context of nature development programmes.